Compacted fabrics for orthopedic casting tapes

ABSTRACT

The present invention provides an article, comprising: a fabric sheet which has been compacted using a heat shrink yarn; and a curable or hardenable resin coated onto the fabric sheet. The present invention involves compacting a fabric sheet to impart stretchability and conformability to the fabric while minimizing undesirable recovery forces. Suitable fabrics for compacting are fabrics which comprise fiberglass fibers which are capable of first being compacted and then being heat set or annealed in the compacted state. The article may be in the form of an orthopedic bandage and may optionally contain a micro fiber filler associated with the resin.

This is a division of application Ser. No. 08/141/830 filed Oct. 25,1993 now U.S. Pat. No. 5,455,060.

FIELD OF THE INVENTION

This invention relates to sheet materials coated with a curable orhardenable polymeric resin. More particularly, this invention relates toa curable or hardenable resin coated sheet material useful in preparingan orthopedic bandage.

BACKGROUND OF THE INVENTION

Many different orthopedic casting materials have been developed for usein the immobilization of broken or otherwise injured body limbs. Some ofthe first casting materials developed for this purpose involve the useof plaster of Paris bandages consisting of a mesh fabric (e.g., cottongauze) with plaster incorporated into the openings and onto the surfaceof the mesh fabric.

Plaster of Paris casts, however, have a number of attendantdisadvantages, including a low strength-to-weight ratio, resulting in afinished cast which is very heavy and bulky. Furthermore, plaster ofParis casts typically disintegrate in water, thus making it necessary toavoid bathing, showering, or other activities involving contact withwater. In addition, plaster of Paris casts are not air permeable, thusdo not allow for the circulation of air beneath the cast which greatlyfacilitates the evaporation and removal of moisture trapped between castand skin. This often leads to skin maceration, irritation, or infection.Such disadvantages, as well as others, stimulated research in theorthopedic casting art for casting materials having improved propertiesover plaster of Paris.

A significant advancement in the art was achieved when polyisocyanateprepolymers were found to be useful in formulating a resin fororthopedic casting materials, as disclosed, for example, in U.S. Pat.No. 4,502,479 (Garwood et al.) and U.S. Pat. No. 4,441,262 (Von Bonin etal.). U.S. Pat. No. 4,502,479 sets forth an orthopedic casting materialcomprising a knit fabric which is made from a high modulus fiber (e.g.,fiberglass) impregnated with a polyisocyanate prepolymer resin whichwill form a polyurea. Orthopedic casting materials made in accordancewith U.S. Pat. No. 4,502,479 provide significant advancement over theplaster of Paris orthopedic casts, including a higher strength-to-weightratio and greater air permeability. However, such orthopedic castingmaterials tend not to permit tactile manipulation or palpation of thefine bone structure beneath the cast to the extent possible whenapplying a plaster of Paris cast. In this regard, knit fiberglassmaterials are not as compressible as plaster, and tend to mask the finestructure of the bone as the cast is applied, e.g., the care providermay be limited in "feeling" the bone during reduction of the fracture.

Fiberglass backings have further disadvantages. For example, fiberglassbackings are comprised of fibers which have essentially no elongation.Because the fiber elongation is essentially nil, glass fabrics do notstretch unless they are constructed with very loose loops which candeform upon application of tension, thereby providing stretching of thefabric. Knitting with loosely formed chain stitches impartsextensibility by virtue of its system of interlocking knots and looseloops.

To a greater extent than most knitted fabrics, fiberglass knits tend tocurl or fray at a cut edge as the yarns are severed and adjacent loopsunravel. Fraying and raveling produce unsightly ends and, in the case ofan orthopedic cast, frayed ends may interfere with the formation of asmooth cast, and loose, frayed ends may be sharp and irritating afterthe resin thereon has cured. Accordingly, frayed edges are considered adistinct disadvantage in orthopedic casting tapes. Stretchy fiberglassfabrics which resist fraying are disclosed in U,S. Pat. No. 4,609,578(Reed), the disclosure of which is incorporated by reference for itsteaching of heat-setting. Thus, it is well known that fraying offiberglass knits at cut edges can be reduced by passing the fabricthrough a heat cycle which sets the yarns giving them newthree-dimensional configurations based on their positions in the knit.When a fiberglass fabric which has been heat-set is cut, there isminimal fraying and when a segment of yarn is removed from the heat-setfabric and allowed to relax, it curls into the crimped shape in which itwas held in the knit. Accordingly, at the site of a cut, the severedyarns have a tendency to remain in their looped or knotted configurationrather than to spring loose and cause fraying.

In processing extensible fiberglass fabrics according to U.S. Pat. No.4,609,578 (Reed), a length of fabric is heat-set with essentially notension. The fabric is often wound onto a cylindrical core so largebatches can be processed at one time in a single oven. Care must betaken to avoid applying undue tension to the fabric during wind-up onthe knitter which would distort the knots and loops. To prevent applyingtension to the fabric during winding, the winding operation ispreferably performed with a sag in the fabric as it is wound on thecore.

Alternatively, U.S. Pat. No. 5,014,403 (Buese) describes a method ofmaking a stretchable orthopedic fiberglass casting tape by knitting anelastic yarn under tension into the fiberglass fabric in the lengthdirection, releasing the tension from the elastic yarn to compact thefabric and removing the elastic yarn from the fabric. The resultingfabric must then be collected under low tension in order to preserve thecompact form. Likewise, any subsequent heat setting must also beperformed under low tension. However, to avoid exceeding this lowtension is difficult and as a result substantial amounts of thecompaction imparted by the elastomeric yarn may be lost duringsubsequent processes. The elastic yarn is removed by a combustionprocess which may cause localized areas of high temperature which maydegrade the fiberglass yarns. The physical properties of glass fibersare adversely affected when subjected to temperatures in excess of about540° C. Heating fiberglass fabrics to temperatures above about 540° C.should be avoided, as subjecting the fiberglass to temperatures ofgreater than about 540° C. can weaken the fiberglass yarns in thefabric, which may result in reduced strength of casts made from suchfabrics.

From the foregoing, it will be appreciated that what is needed in theart is an orthopedic casting material which has both the advantages ofplaster of Paris, e.g., good moldability and palpability of the finebone structure, and the advantages of non-plaster of Paris materials,e.g., good strength-to-weight ratio and good air permeability. In thisregard it would be a significant advancement in the art to provide sucha combination of advantages without actually using plaster of Paris,thereby avoiding the inherent disadvantages of plaster of Paris outlinedherein. It would be a further advancement in the art to provide suchnon-plaster of Paris orthopedic casting materials which have as good orbetter properties than the non-plaster of Paris orthopedic castingmaterials of the prior art. Such orthopedic casting materials andmethods for preparing the same are disclosed and claimed herein.

RELATED APPLICATIONS

Of related interest are the following U.S. patent applications, filed onJan. 25, 1993 by the assignee of this invention: "Mechanically CompactedFabrics for Orthopedic Casting Tapes" --Ser. No. 08/008,161; and"Microcreping of Fabrics for Orthopedic Casting Tapes" --Ser. No.8/008,751; and copending U.S. patent application filed on even dateherewith by the assignee of this invention entitled "Wet Compacting ofFabrics for Orthopedic Casting Tapes" --Ser. No. 08/142573, and"Vibration Compacted Fabrics for Orthopedic Casting Tapes, Ser. No.08/142,177, which are herein incorporated by reference.

SUMMARY OF THE INVENTION

The present invention provides an article comprising a compactedfiberglass fabric sheet and a curable or hardenable resin coated ontothe fabric sheet. The fabric sheet is compacted using a heat shrinkableyarn (hereinafter "heat shrink yarn") and is optionally heat set therebyremoving the heat shrink yarn and providing extensibility to the fabric.The article may be in the form of an orthopedic bandage. The presentinvention also provides an article comprising a compacted fiberglassfabric sheet, a heat shrink yarn, and a curable or hardenable resincoated onto the fabric sheet. The heat shrink yarn in this embodimentremains in the fabric, thereby providing resistance to lengthwiseextension, yet yields in response to a tensile force thereby providing acontrolled extension of the fabric.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a two bar Raschel knit in which bar one performs a simplechain stitch and bar two performs lapping motions to lay in yarn.

FIG. 2 is a three bar Rasehel knit in which bar one performs a simplechain stitch and bars two and three perform lapping motions to lay inyarn, and wherein bar three illustrates the lay in of a heat shrinkyarn.

FIG. 3 is a four bar Raschel knit in which bar one performs a simplechain stitch and bars two, three and four perform lapping motions to layin yarn, and wherein bar four illustrates the lay in of a heat shrinkyarn.

FIG. 4 is a depiction of a three bar Raschel knit in which bar oneperforms a simple chain stitch, bar two performs lapping motion to layin yarn, and bar three performs lapping motions to lay in a heat shrinkyarn. The bars are depicted in a overlapping view.

FIG. 5 is a depiction of a three bar "latch hook" Raschel knitter inwhich four needles are shown knitting four chain stitches and twoguidebars providing lay-in yarns. For the purposes of this invention,one might alternatively employ a "compound needle" Raschel knitter whichis not shown.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to orthopedic casting materials andmethods for preparing and using such orthopedic casting materials,wherein the materials comprise a fiberglass backing or fabric which isimpregnated with a curable or hardenable liquid resin. In particular,the fabrics employed in the present invention have importantcharacteristics and physical properties which allow the fabrics to bemade highly extensible.

One element of this invention is a flexible sheet upon which a curableor hardenable resin can be coated to reinforce the sheet when the resinis cured or hardened thereon. The sheet is preferably porous such thatthe sheet is at least partially impregnated with the resin. Examples ofsuitable sheets are knit fabrics comprised of inorganic fibers ormaterials such as fiberglass. It is presently believed that this processwill work for a variety of high modulus materials including fiberglass,ceramic fibers such as Nextel™, and polyaramides fibers such as Kevlar.The sheet may alternatively be referred to as the "scrim" or the"backing."

The term "high modulus" as used herein to describe the fabric componentof the casting material refers to the degree of resistance todeformation or bending and is expressed in terms of the modulus ofelasticity. Modulus of elasticity is the ratio of change in stress tothe change in strain which occurs when a fiber is mechanically loaded.The initial modulus of elasticity of the fiber should be greater thanabout 8×10⁶ lbs/square inch (55.2 GPa). Such fibers include continuousfilament E-fiberglass, polyaramid filament known as Kevlar® 49(available from E.I. DuPont de Nemours and Company), ceramic fibers suchas Nextel® (available from 3M Company), continuous filament graphitesuch as Thornel® (available from Union Carbide Corp.), boron fiber (suchas made by Avco Corp.), and metal fibers such as stainless steelfilaments which when fine enough can be formed into fabrics by weavingor knitting. These high modulus fibers impart a high degree of strengthand rigidity to the cast. They may be combined with low to intermediatemodulus materials when the flexibility of such yarns enables easierfabrication of the fabric. Low modulus fibers are those having aninitial modulus of elasticity of less than about 3×10⁶ lbs/in² (20.7GPa) and include cotton, polyester (such as "Dacron"), polypropylene,"Orion", "Dynel"® (Union Carbide), "Nomex"® (Dupont) and nylon.

The present invention involves compacting a fabric sheet using a heatshrink yarn to impart stretchability and conformability to the fabricwhile minimizing undesirable recovery forces.

Suitable fabrics, after compaction, have important characteristics andphysical properties which allow the fabrics to be loaded with resin tothe extent needed to provide proper strength as an orthopedic castingmaterial, while providing necessary porosity as well as improvedextensibility leading to improved conformability, tactilemanipulability, moldability, and palpability. Several important criteriafor choosing a fabric which will provide the characteristics necessaryfor purposes of the present invention include: (1) lengthwiseextensibility and conformability after compaction, and the relatedcharacteristics of moldability, tactility, and palpability once thefabric has been resin impregnated; (2) resin loading capacity; and (3)porosity. It is important that each of these parameters be carefullycontrolled in providing fabrics which will successfully form orthopediccasting materials (e.g., casts having high strength and goodlayer-to-layer lamination strength) within the scope of the presentinvention.

Extensibility is important from the standpoint that the fabric must beextensible enough along its length, i.e., in the elongated direction, sothat the resultant orthopedic casting material can be made tosubstantially conform to the body part to which it is applied. Materialswhich are not sufficiently extensible in the elongated direction do notconform well to the body part when wrapped therearound, often resultingin undesirable wrinkles or folds in the material. On the other hand, theextensibility of the fabric in the elongated direction should not be sohigh that the material is too stretchy, resulting in a materialstructure which may be deformed to the extent that strength issubstantially reduced.

For purposes of the present invention, the coated fabric, aftercompaction and after being coated with a curable liquid resin, shouldhave from about 10% to about 200% extensibility in the elongateddirection when a 2.63N tensile load or force is applied per 1 cm widesection of the fabric, and preferably from about 25% to about 100%extensibility in the elongated direction when a 2.63N tensile load orforce is applied per 1 cm wide section of the fabric, and morepreferably from about 35% to about 65% extensibility in the elongateddirection when a 268 gram load or force is applied across a 1 cm sectionof the fabric.

Although not nearly as critical, it is also desirable that the fabricemployed have some extensibility along its width, i.e., in the directiontransverse to the elongated direction. Thus although the fabric may havefrom 0% to 100% extensibility in the transverse direction, it ispresently preferable to use a fabric having from about 1% to about 30%extensibility in the transverse direction when a 2.63N tensile load orforce is applied per 1 cm wide section of the fabric. The compactionprocess described herein principally imparts extensibility in theelongated direction. However, it is anticipated that one might compact afabric in the elongated direction and in the transverse direction,thereby imparting biaxial extensibility.

The fabrics of the present invention, after compaction, althoughstretchable, are preferably not overly elastic or resilient. Fabricswhich are overly elastic, when used as backings for orthopedic bandages,tend to cause undesirable constriction forces around the wrapped limb orbody part. Thus, once the resin impregnated fabric has been stretchedand applied around a body part, the stretched material preferablymaintains its shape and does not resort back to its unstretehedposition.

The resin loading capacity or ability of the fabric to hold resin isimportant from the standpoint of providing an orthopedic castingmaterial which has sufficient strength to efficaciously immobilize abody part. The surface structure of the fabric, including the fibers,interstices, and apertures, is very important in providing proper resinloading for purposes of the present invention. In this regard, theinterstices between the fibers of each fiber bundle must providesufficient volume or space to hold an adequate amount of resin withinthe fiber bundle to provide the strength necessary; While at the sametime, the apertures between fiber bundles preferably remain sufficientlyunoccluded such that adequate porosity is preserved once the cast isapplied. Thus, the interstices between fibers are important in providingthe necessary resin loading capacity, while the apertures are importantin providing the necessary porosity for the finished cast. However, abalancing of various parameters is needed to achieve both proper resinloading and porosity. The coated fabric should have preferably betweenabout 6 and 70 openings (i.e., apertures) per square cm, more preferablybetween about 10 and 50 openings per square cm, and most preferablybetween about 20 and 40 openings per square cm when measured under atensile load of 2.63N/cm width. As used herein an "opening" is definedas the area defined by adjacent wales and in-lay members. The number ofopenings per unit area is therefore determined by multiplying the numberof wales by the number of courses and dividing by the

As used herein, a "compacted" fiberglass sheet is one in whichextensibility is imparted to the fabric due to the structuraloverlapping of successive loops and/or the structural relaxation ofloops by the "heat shrink yarn" compaction processes described herein.The compaction process is believed to impart extensibility to the fabricby "compacting" the loops of the knit as described herein. Typically,when a fabric is knitted the inside surfaces of two adjacent rows ofloops are in contact or nearly in contact and the loops are distorted inthe lengthwise direction (e.g., in the shape of an oval). This contactand/or distortion is the result of the fabric being under tension whilethe knit is being formed. Each successive row of loops (i.e., chainstitches) is, in effect, formed against the preceding row of loops. Thecompaction process of the present invention imparts fabric compaction byoverlapping adjacent rows of loops (i.e., to a "non-contacting"position) and/or relaxing the strained loops to a lower stress (e.g.,more circular) configuration and optionally setting or annealing thefabric in the compacted form. Extensibility is imparted to the fabricdue to the overlap of the rows and/or the greater ability of the morecircular loops to be deformed. When tension is again applied to thefabric the loops can return to their original "contacting" position,i.e., the position they occupied when originally knit.

Fiberglass knitted fabrics with good extensibility are achievable withtwo common knitting method: Raschel and tricot. Raschel knitting isdescribed in "Raschel Lace Production" by B. Wheatley (published by theNational Knitted Outerwear Association, 51 Madison Avenue, New York,N.Y. 10010) and "Warp Knitting Production" by Dr. S. Raz (published byHeidelberger Verlagsanstadt und Druckerei GmbH, Hauptstr. 23, D-6900Heidelberg, Germany). Two, three and four bar Raschel knits can beproduced by regulating the amount of yarn in each stitch. Orthopediccasting tape fabrics are generally two bar Raschel knits although extrabars may be employed. Factors which affect the extensibility offiberglass Raschel knits are the size of the loops in the "chain"stitch, especially in relation to the diameter(s) of the yarn(s) whichpasses through them, and the amount of a loose yarn in the "lay-in" or"laid-in" stitch(es). If a chain loop is formed and two strands oflay-in yarn pass through it which nearly fill the loop, then the loopresists deformation and little stretch will be observed. Conversely, ifthe lay-in yarns do not fill the loop, then application of tension willdeform the loop to the limits of the lay-in yarn diameter and stretchwill be observed.

Typical bar patterns for the knit fabric substrates of the presentinvention are shown in the drawings.

FIG. 1 is a two bar Raschel knit in which bar one performs a simplechain stitch and bar twp performs lapping motions to lay in yarn.

FIG. 2 is a three bar Raschel knit in which bar one performs a simplechain stitch and bars two and three perform lapping motions to lay inyarn, and wherein bar three illustrates the lay in of a heat shrinkyarn.

FIG. 3 is a four bar Raschel knit in which bar one performs a simplechain stitch and bars two, three and four perform lapping motions to layin yarn, and wherein bar four illustrates the lay in of a heat shrinkyarn.

FIG. 4, is a depiction of a three bar Raschel knit in which bar oneperforms a simple chain stitch, bar two performs lapping motion to layin yarn, and bar three performs lapping motions to lay in a heat shrinkyarn. The bars are depicted in a overlapping view.

FIG. 5 is a depiction of a three bar "latch hook" Raschel knitter inwhich four needles are shown knitting four chain stitches and two lay-institches. For the purposes of this invention, one might alternativelyemploy a "compound needle" Rasehel knitter which is not shown.

It should be understood that the above bar patterns may be modified. Forexample, FIG. 2 may be modified by employing fewer or more heat shrinklay-in yarns. Alternatively, the heat shrink yarn may be knitted in oneor more of the chain stitches of the fabric or more than one heat shrinkyarns may be laid in a single chain stitch.

For orthopedic casting material, the fabric selected (preferablyfiberglass), in addition to having the extensibility requirement notedabove, should be of a suitable thickness and mesh size to insure goodpenetration of the curing agent (e.g., water) into the roll ofresin-coated tape and to provide a finished cast with adequate strengthand porosity. Such fabric parameters are well-known to those skilled inthe art and are described in U.S. Pat. No. 4,502,479 which is hereinincorporated by reference.

When the casting material is a fiberglass fabric, suitable heat shrinkyarns are made of fibers which shrink and optionally cornbust attemperatures lower than the degradation temperature of the inorganicfibers (e.g., glass fibers) of the fabric. Preferably the shrinkage andcombustion temperatures of the heat shrink yarn are less than or equalto the temperature commonly used for heat setting fiberglass yarns. Morepreferably the shrinkage temperature of the heat shrink yarn is betweenabout 70° C. and 300° C. Most preferably the shrinkage temperature ofthe heat shrink yarn is between about 100° C. and 200° C. Preferably thecombustion temperature of the heat shrink yarn is between about 200° C.and 540° C. More preferably the combustion temperature of, the heatshrink yarn is between about 300° C. and 500° C. Heating the fabric totemperatures above about 540° C. should be avoided as subjecting thefiberglass to temperatures of greater than about 540° C. can weaken thefiberglass yarns in the fabric which may result in reduced strength ofcasts made from such fabrics.

Suitable heat shrink yarns for use in the present invention includeyarns which shrink when heated at a temperature less than thedegradation temperature of the inorganic fabric and which when presentin a sufficient quantity are capable of compacting the fabric. Preferredheat shrink yarns comprise fibers having at least 10% shrinkage whenheated (and when tested using a Testrite MK4 tester as described inExample 1). More preferably, the yarn has at least 20% shrinkage aridmost preferably at least 30% shrinkage.

One class of suitable heat shrink yarns are partially or highly orientedpolymer yarns which shrink when heated above their glass transitiontemperature but below their melting temperature. In general, thephysical properties of polymer fibers (e.g., polyester fibers) isstrongly affected by fiber structure. For example, to provide the heatshrink property some degree of crystallinity is preferred.

Suitable polymer fibers for use as the heat shrink yarn include bothmultifilament and monofilament (staple or continuous filament) yarnswhich are optionally texturized and fully or partially oriented. Theyarns may be comprised of semi-crystalline polymers such as polyester,polyamide, polyethylene and copolymers or graft. copolymers of these.Preferred polymer fibers for use as the heat shrink yarninclude-polyester and polyethylene. Partially oriented polyester ispresently most preferred.

The heat shrink yarn(s) may be knit into the fabric either as a lay-inor as a chain stitch. Preferably, the heat shrink yarn is knit into thefabric as a layin stitch. The essential requirements of a heat shrinkyarn are that it be capable of knitting with the fabric yarn and that itcompact the fabric. Therefore, when the heat shrink yarn is shrunk andoptionally combusted, e.g., through application of, heat, the fabricremains present in the form of a compacted, optionally heat set fabric.The heat shrink yarn is preferably knit into the fabric such that theknit is compacted at least 10%, more preferably at least 14%, and mostpreferably at least 18%.

When the heat shrink yarn is present as laid-in yarns it is preferablyknitted through a single wale. This embodiment is illustrated, forexample, in FIG. 2. In that figure, a third bar is depicted knitting aheat shrink yarn across a single chain stitch (bar 1). Additional lay-inyarns are knitted into the fabric using bar 2. In this manner maximumlengthwise compaction may be achieved as the heat shrink yarn is shrunk.Alternatively, the heat shrink yarn may cross more than one chainstitch. It is believed that this embodiment will produce a fabric withbiaxial compaction.

As previously mentioned, the heat shrinkable yarn should be positionedin the knit so as to minimize the amount required and maximize the forcegenerated during contraction. If the yarn is placed in as a wale inaddition to the fiberglass wales (i.e., as an additional wale sinceafter desizing some wales would need to be present) a significant amountof organic material is added which could result in a brittle tape afterheat treatment. If the yarn is placed as a lay-in and maximum lengthwisecompaction is desired then the yarn is preferably laid in across asingle needle in order to ensure that most of the shrinkage force of thelaid-in yarn is used to compact the tape in the length direction.

The heat shrink yarn may be knitted through each wale (not shown in FIG.2) or through fewer than all the wales (as shown in FIG. 2). Notably,there need not be a heat shrink yarn for every wale. The heat shrinkyarn need only be present in the fabric in an amount sufficient to givethe desired compaction to the fabric when the yarn is heat shrunk. Ithas been found that knitting the heat shrink yarn through every fourthor fifth wale is preferred. Having too many heat shrink yarns increasesthe potential for undesirable localized heating of the fiberglass duringthe optional combustion step. Having too few heat shrink yarns resultsin uneven compaction or inadequate compaction. The exact number of heatshrink yarns needed will depend upon the fabric weight and knit patternemployed, the weight and shrink properties of the heat shrink yarnemployed, and the desired amount of compaction.

The heat shrink yarn may also be in the form of a chain stitch yarn.When the heat shrink yarn is knitted in the form of a chain stitch it ispreferable to lay in noncombustible yarns (e.g., fiberglass yarns)across the heat shrink chain stitch yarn and thereby connect adjacentnoncombustible chain stitches. Thus, if the heat shrink chain stitch islater optionally removed when heat setting the fiberglass, the fabricwill maintain its integrity.

It may also be beneficial to vibrate the fabric during the compactionprocess to improve the uniformity of the compaction. This isparticularly important when the heat shrink yarns are spaced apart andnot knit through every wale. Suitable vibration methods are described incopending U.S. patent application Ser. No. 08/142,177. "VibrationCompacted Fabrics for Orthopedic Casting Tapes",

In processing the knitted fiberglass fabric of the present invention, alength of fabric is optionally, and preferably, heat-set while thefabric is in a compacted form. Preferably, the fabric is compacted andthen wound onto a cylindrical core so large batches can be heat set atone time in a single oven. Care must be taken to avoid applying unduetension to the fabric (after combustion of the heat shrink yarn andbefore the heat set has occurred) which would distort the knots andloops.

A continuous heat-setting process may also be used in which a length offabric is first compacted by heat shrinking the heat shrink yarn andthen the compacted fabric is placed on a moving conveyor system andpassed through an oven for a sufficient time and temperature to achieveheat setting of the fabric. Alternatively, one may use the same oven toboth compact the fabric and heat set the fiberglass yarns provided thatsufficient time is allowed for the compaction process prior to meltingof the heat shrink yarn. Notably, when short lengths of fabric are soprocessed the ends of the heat shrink yarn should be held in relation tothe ends of the fiberglass yarns so as to cause compaction. Otherwisethe heat shrink yarns may merely slip against the fabric as they shrinkand not cause compaction of the knit fabric.

The heat-setting step may be performed in a number of conventional waysknown to the art. In heat-setting a small piece of fiberglass fabric,e.g., 25 centimeters of tape, in a single layer, a temperature of 425°C. for three minutes has been found to be sufficient. Equivalent settingat lower temperatures is possible, but longer time is required. Ingeneral, batch processes require a longer residence time at the selectedtemperature due to the mass of glass fabric which must be heated and theneed to remove all traces of sizing material which may undesirably colorthe final fabric.

The optimum heat-setting process described above is sufficient in mostcases to remove the sizing from the fabric. However, the process of thepresent invention may also be practiced using partially heat-desized ora chemically-desized fabric. Chemical desizing processes are describedin U.S. Pat. Nos. 3,686,725; 3,787,272; and 3,793,686. Heat desizingprocesses are described in U.S. Pat. No. 4,609,578.

In general, to completely desize the fiberglass tape and not leave anyvisible residue it is necessary to heat the tape to a temperaturebetween 370° and 430° C. more preferably between 400° C. and 430° C. Thecloser you get to 430° C. the shorter the cycle and more efficient theoperation. Although the tape could be cleaned at higher temperatures,this may cause permanent degradation of the fiberglass fabric. Forexample, when the temperature of the fabric exceeds 480° C. andespecially when the temperature exceeds 540° C. the tensile strength ofthe knit decreases very rapidly. When the tape is exposed totemperatures over 590° C it becomes very brittle and wrapping a castusing normal tension is precluded. A preferred heat desizing cycleraises the oven temperature to about 430° C. and maintains thattemperature until the tape is clean (e.g., about 6-8 hours in arecirculating oven). However, obtaining this result is somewhatcomplicated since the tape's temperature is affected by both the heat ofthe oven and the heat of combustion resulting from burning the sizingand/or any organic yarn (i.e., the heat shrink yarn) which may bepresent.

Controlling the exotherm from organic material in the knit is essentialand can be accomplished most easily and economically by limiting thetotal amount of added organic material (e.g., sizing and heat shrinkyarn) which must be removed. In order to knit a fiberglass yarn withoutexcessive damage a sizing is preferably present. Preferably the amountof sizing utilized is the minimum level necessary to prevent damageduring knitting. A preferred amount of sizing on fiberglass is between0.75 and 1.35% (based on weight of the fabric). In addition to thissizing, in order to compact the tape, a heat shrinkable yarn is added tothe fabric. Since this yarn adds substantially to the total level oforganic material in the fabric it is important to limit the amountadded. This can be accomplished by several methods.

First, one may limit the number of heat shrink yarns used. Initialtrials at compacting fabrics using the method of the present inventionplaced the heat shrink yarn in every wale. This amount of heat shrinkyarn is believed to be unnecessary and undesirable due to the resultinghigh exothermic temperature during desizing. Preferably the knit has aheat shrinkable yarn in-laid across the tape only in wales spaced 2-6needles apart. Most preferably the knit has a heat shrinkable yarnin-laid across the tape only in wales spaced 3 to 6 needles apart.Normally, the spacing is uniform across the web but since the preferredpattern used crosses only a single needle it can be varied withoutmodification to the knitting machine.

Second, one may decrease the denier of the heat shrink yarn. Preferably,the lowest denier yarn which has sufficient shrink force to compact thetape should be used. For preferred fiberglass fabrics the preferred heatshrink yarns are about 100 to 500 denier, more preferably about 200 to300 denier.

Finally, it has been observed that the jumbo's winding tension cangreatly influence the exothermic temperature rise due to combustion andtherefore adversely affect web integrity. In general, jumbos wound underhigher tension tend to reach a lower peak temperature and have a greaterweb integrity than those wound more loosely. It is believed that theorganic content of more tightly wound jumbos burn more slowly andtherefore the jumbos have lower peak internal temperatures. While notintending to be bound by theory, this result is believed to be due tooxygen starvation within the jumbo. Within a jumbo (i.e., away from thesurface of the roll) the availability of oxygen is controlled by thediffusion rate into the jumbo. Careful control of the roll'spermeability to oxygen can be utilized to control the rate of combustionof the organic material.

The fabric is preferably cooled prior to application of the resin. Theresin selected to apply to the heat-set fabric is dictated by theend-use of the product. For orthopedic casting materials, suitableresins are well-known and described for example, in U.S. Pat. Nos.4,376,438; 4,433,680; 4,502,479; and 4,667,661 and U.S. patentapplication Ser. No. 07/376,421 which are herein incorporated byreference. The presently most preferred resins are the moisture-curableisocyanate-terminated polyurethane prepolymers described in theaforementioned patents. Alternatively, one may employ one of the resinsystems described herein. The amount of such resin applied to thefiberglass tape to form an orthopedic casting material is typically anamount sufficient to constitute 35 to 50 percent by weight of the final"coated" tape. The term "coated" or "coating" as used herein withrespect to the resin refers generically to all conventional processesfor applying resins to fabrics and is not intended to be limiting.

To insure storage stability of the coated tape, it must be properlypackaged, as is well known in the art. In the case of water-curableisocyanate-terminated polyurethane prepolymer resin systems, moisturemust be excluded. This is typically accomplished by sealing the tape ina foil or other moisture-proof pouch.

In one embodiment of the present invention, a fiberglass fabric whichfurther comprises a plurality of hut shrink yarns is knit according tothe process described herein, compacted by heat shrinking theaforementioned yarns, and then heat set in the compacted form while alsoremoving the heat shrink yarns. The compacted fabric is then coated witha curable resin. There are many advantages to this process overconventional knitting processes. First, unlike traditional uncompactedknit fiberglass fabrics, the fabric produced by this method hasincreased extensionability. Furthermore, the heat shrink yarn, when inits shrunken state, provides support to the fabric during subsequentcollecting operations (such as when winding a large jumbo roll) therebypreventing undesirable extension of the fabric prior to it being heatset. The finished fabric of this embodiment comprises onlynoncombustible yarns and retains its compacted form as a result of theheat setting of the fiberglass yarns.

In a second embodiment of the present invention, a fiberglass fabricwhich further comprises a plurality of heat shrink yarns is knitaccording to the process described herein and compacted by heatshrinking the aforementioned yarns. The compacted fabric is then coatedwith a curable resin. There are many advantages to this process overconventional knitting processes. First, unlike traditional uncompactedknit fiberglass fabrics, the fabric produced by this method hasincreased extensibility. The heat shrink yarn, when in its shrunkenstate, provides support to the fabric during subsequent windingoperations (such as when winding a roll during the production process)and unwinding operations (such as when the fabric is applied to thepatient) thereby preventing undesirable extension of the fabric prior toit being applied. The finished fabric of this embodiment retains itscompacted form principally as a result of the heat shrink yarns and isextensible only when the heat shrink yarns are plastically deformed(e.g., by stretching them). That is to say, the fiberglass fabric may beextended, as needed, when it ii applied to the patient by stretching(and thereby plastically deforming) the heat shrunken yarns. In contrastto stretching an elastic yarn, plastically deforming a heat shrink yarnavoids undesirable rebound of the fabric which could cause undesirableconstriction forces. Rather, the plastically deformed heat shrink yarnsretain their deformed state when the tensile force is removed.

Suitable fabrics, after compaction, are compacted to between about 30and 90 percent of their original dimension. More preferably, the fabricis compacted to between about 50 and 80 percent of its originaldimension. Most preferably, the fabric is compacted to between about 60and 75 percent of its original dimension.

The curable or hardenable resins useful in this invention are resinswhich can be used to coat a sheet material and which can then be curedor hardened to reinforce the sheet material. For example, the resin iscurable to a crosslinked thermoset state. The preferred curable orhardenable resins are fluids, i.e., compositions having viscositiesbetween about 5 Pa s and about 500 Pa s, preferably about 10 Pa s toabout 100 Pa s.

The resin used in the casting material of the invention is preferablyany curable or hardenable resin which will satisfy the functionalrequirements of an orthopedic cast. Obviously, the resin must benontoxic in the sense that it does not give off significant amounts oftoxic vapors during curing which may be harmful to either the patient orthe person applying the cast and also that it does not cause skinirritation either by chemical irritation or the generation of excessiveheat during cure. Furthermore, the resin must be sufficiently reactivewith the curing agent to insure rapid hardening of the cast once it isapplied but not so reactive that it does not allow sufficient workingtime to apply and shape the cast. Initially, the casting material mustbe pliable and formable and should adhere to itself. Then in a shorttime following completion of cast application, it should become rigidor, at least, semi-rigid, and strong to support loads and stresses towhich the cast is subjected by the activities of the wearer. Thus, thematerial must undergo a change of state from a fluid-like condition to asolid condition in a matter of minutes.

The preferred resins are those cured with water. Presently preferred areurethane resins cured by the reaction of a polyisocyanate and a polyolsuch as those disclosed in U.S. Pat. No. 4,131,114. A number of classesof water-curable resins known in the art are suitable, includingpolyurethanes, cyanoacrylate esters, epoxy resins (when combined withmoisture sensitive catalysts), and, prepolymers terminated at their endswith trialkoxy- or trihalosilane groups. For example, U.S. Pat. No.3,932,526 discloses that bis(perfluoromethylsulfonyl)-2-aryl ethylenescause epoxy resins containing traces of moisture to become polymerized.

Resin systems other than those which are water-curable may be used,although the use of water to activate the hardening of an orthopediccasting tape is most convenient, safe and familiar to orthopedicsurgeons and medical casting personnel. Resin systems such as thatdisclosed in U.S. Pat. No. 3,908,644 in which a bandage is impregnatedwith difunctional acrylates or methacrylates, such as thehis-methacrylate ester derived from the condensation of glycidylmethacrylate and bisphenol A (4,4'-isopropylidenediphenol) are suitable.The resin is hardened upon wetting with solutions of a tertiary amineand an organic peroxide. Also, the water may contain a catalyst. Forexample, U.S. Pat. No. 3,630,194 proposes an orthopedic tape impregnatedwith acrylamide monomers whose polymerization is initiated by dippingthe bandage in an aqueous solution of oxidizing and reducing agents(known in the art as a redox initiator system). The strength, rigidityand rate of hardening of such a bandage is subjected to the factorsdisclosed herein. Alternatively, hardenable polymer dispersions such asthe aqueous polymer dispersion disclosed in U.S. Pat. No. 5,169,698,which is herein incorporated by reference, may be used in the presentinvention.

Some presently more preferred resins for use in the present inventionare water-curable, isocyanate-functional prepolymers. Suitable systemsof this type are disclosed, for example, in U.S. Pat. No. 4,411,262, andin U.S. Pat. No. 4,502,479. Preferred resin systems are disclosed inU.S. Pat. No. 4,667,661 and U.S. patent application Ser. No. 07/376,421.The following disclosure relates primarily to the preferred embodimentof the invention wherein water-curable isocyanate-functional prepolymersare employed as the curable resin. A water-curable isocyanate-functionalprepolymer as used herein means a prepolymer derived frompolyisocyanate, preferably aromatic, and a reactive hydrogen compound oroligomer. The prepolymer has sufficient isocyanate-functionality to cure(i.e., to set or change from a liquid state to a solid state) uponexposure to water, e,g., moisture vapor, or preferably liquid water.

It is preferred to coat the resin onto the fabric as a polyisocyanateprepolymer formed by the reaction of an isocyanate and a polyol.Suitable isocyanates include 2,4-toluene diisocyanate, 2,6-toluenediisocyanate, mixture of these isomers, 4,4'-diphenylmethanediisocyanate, 2,4'-diphenylmethane diisocyanate, mixture of theseisomers together with possible small quantities of 2,2'-diphenylmethanediisocyanate (typical of commercially available diphenylmethanediisocyanate), and aromatic polyisocyanates and their mixtures such asare derived from phosgenation of the condensation product of aniline andformaldehyde. It is preferred to use an isocyanate which has lowvolatility such as diphenylmethane diisocyanate (MDI) rather than a morevolatile material such as toluene diisocyanate (TDI). Typical polyolsfor use in the prepolymer system include polypropylene ether glycols(available from Arco Chemical Co. under the trade name Arcol™ PPG andfrom BASF Wyandotte under the trade name Pluracol™), polytetramethyleneether glycols (Polymeg™ from the Quaker Oats Co.), polycaprolactonediols (Niax™ PCP series of polyols from Union Carbide), and polyesterpolyols (hydroxyl terminated polyesters obtained from esterification ofdicarboxylic acids and diols such as the Rucoflex™ polyols availablefrom Ruco division, Hooker Chemical Co.). By using high molecular weightpolyols, the rigidity of the cured resin can be reduced.

An example of a resin useful in the casting material of the inventionuses an isocyanate known as Isonate™ 2143L available from the UpjohnCompany (a mixture containing about 73% of MDI) and a polypropyleneoxide polyol from Arco known as Arcol™ PPG725. To prolong the shelf lifeof the material, it is preferred to include from 0.01 to 1.0 percent byweight of benzoyl chloride or another suitable stabilizer.

The reactivity of the resin once it is exposed to the water curing agentcan be controlled by the use of a proper catalyst. The reactivity mustnot be so great that: (1),a hard film quickly forms on the resin surfacepreventing further penetration of the water into the bulk of the resin;or (2) the cast becomes rigid before the application and shaping iscomplete. Good results have been achieved using4-[2-[1-methyl-2-(4-morpholinyl)ethoxy]ethyl]morpholine (MEMPE) preparedas described in U.S. Pat. No. 4,705,840, the disclosure of which isincorporated by reference, at a concentration of about 0.05 to about 5percent by weight.

Foaming of the resin should be minimized since it reduces the porosityof the east and its overall strength. Foaming occurs because carbondioxide is released when water reacts with isocyanate groups. One way tominimize foaming is to reduce the concentration of isocyanate groups inthe prepolymer. However, to have reactivity, workability, and ultimatestrength, an adequate concentration of isocyanate groups is necessary.Although foaming is less at low resin contents, adequate resin contentis required for desirable cast characteristics such as strength andresistance to peeling. One satisfactory method of minimizing foaming isto add a foam suppressor such as silicone Antifoam A (Dow Corning), orAntifoam 1400 silicone fluid (Dow Corning) to the resin. It isespecially preferred to use a silicone liquid such as Dow CorningAntifoam 1400 at a concentration of about 0.05 to 1.0 percent by weight.Water-curable resins containing a stable dispersion of hydrophobicpolymeric particles, such as disclosed in U.S. patent application Ser.No. 07/376,421 and laid open as European Published Patent ApplicationEPO 0 407 056, may also be used to reduce foaming.

Also included as presently more preferred resins in the presentinvention are non-isocyanate resins such as water reactive liquidorganometallic compounds. These resins are especially preferred as analternative to isocyanate resin systems. Water-curable resincompositions suitable for use in an orthopedic cast consist of awater-reactive liquid organometallic compound and an organic polymer.The organometallic compound is a compound of the formula (R¹ O)_(x) MR²_(y-x) wherein: each R¹ is independently a C₁ -C₁₀₀ hydrocarbon group,optionally interrupted in the backbone by 1-50 nonperoxide --O--, --S--,--C(O)--, or ##STR1## each R² is independently selected from the groupconsisting of hydrogen and a C₁ -C₁₀₀ hydrocarbon group, optionallyinterrupted in the backbone by 1-50 nonperoxide --O--, --S--, --C(O)--,or ##STR2## x is an integer between 1 and y, inclusive; y is the valenceof M; and M is boron, aluminum, silicon, or titanium. The organicpolymer is either an addition polymer or a condensation polymer.Addition polymers are preferably utilized as the organic polymerconstituent. Particularly useful addition polymers are those made fromethylenically unsaturated monomers. Commercially available monomers,from which such addition polymers can be formed, include but are notlimited to, ethylene, isobutylene, 1-hexene, chlorotrifluoroethylene,vinylidene chloride, butadiene, isoprene, styrene, vinyl napthalene,ethyl acrylate, 2-ethylhexyl acrylate, tetrahydrofurfuryl acrylate, poly(ethylene oxide) monoacrylate, heptafluorobutyl acrylate, acrylic acid,methyl methacrylate, 2-dimethylaminoethyl methacrylate,3-methacryloxy-propyltris (trimethylsiloxy)silane, isobutylmethacrylate, itaconic acid, vinyl acetate, vinyl stearate,N,N-dimethylacrylamide, tert-butyl acrylamide, acrylonitrile, isobutylvinyl ether, N-vinyl pyrrolidinone, vinyl azlactone, glycidylmethacrylate, 2-isocyanatoethyl methacrylate, maleic anhydride, vinyltriethoxysilane, vinyl tris(2-methoxyethoxy) silane, and3-(trimethoxysilyl)propyl methacrylate. Polymers beating hydrolyzablefunctionality are preferred. An acidic or basic catalyst may be used toaccelerate the water cure of these compositions. Strong acid catalystsare preferred.

Also included as presently more preferred resins in the instantinvention are alkoxysilane terminated resins, i.e., prepolymers oroligomers, having a number average molecular weight of about 400-10,000,preferably about 500-3,000. A polymer forms upon contacting thealkoxysilane terminated prepolymer with water as a result ofcondensation of molecules of this prepolymer with other molecules of thesame prepolymer. Each molecule of the prepolymer or oligomer contains atleast one hydrolyzable terminal alkoxysilane group. Compounds of FormulaI useful in the resin compositions of the present invention may containone to six terminal alkoxysilane groups per molecule. Preferably, thealkoxysilane terminated resin is a urethane-based resin, i.e., aprepolymer containing --NH--C(O)--O--group(s), or a urea resin, i.e., aprepolymer containing ##STR3## or a resin containing both urea andurethane groups.

The water-reactive alkoxysilane terminated resin having at least onehydrolyzable terminal alkoxysilane group per molecule is preferably acompound of the formula (Formula I): ##STR4## wherein: Q is a polyolresidue;

W is --NH--C(O)--(R² _(2-n-q))--or--X--C(O)--NH--;

X is, ##STR5## --O--, or --S--; Y is, ##STR6## --O--, --S--,carbamylthio (--S--C(O)--NH--), carbamate (--O--C(O)--NH--), orsubstituted or N-substituted ureido (--N(C(O)--NH--)--);

R¹ is a substituted or unsubstituted divalent bridging C₁ -C₂₀₀hydrocarbon group, optionally interrupted in the backbone by 1-50nonperoxide --O--, --C(O)--, --S--, --SO₂ --, --NR⁶ --, amide(--C(O)--NH--), ureido (--NH--C(O)--NH--), carbamate (--O--C(O)--NH--),carbamylthio (--S--C(O)--NH--), unsubstituted or N-substitutedallophonate (--NH--C(O)--N(C(O)--O--)--), unsubstituted or N-substitutedbiuret (--NH--C(O)--N(C(O)--NH)--), and N-substituted isocyanurategroups;

R² can be present or absent, and is selected from the group consistingof H and a substituted or unsubstituted C₁ -C₂₀ hydrocarbon group,optionally interrupted in the backbone by 1-10 nonperoxide--O--,--C(O)--, --S--, --SO₂ --, or NR⁶ --groups;

R³ is a substituted or unsubstituted divalent bridging C₁ -C₂₀hydrocarbon group, optionally interrupted in the backbone by 1-5nonperoxide--O--, --C(O)--, --S--, --SO₂ --, or --NR⁶ --groups;

R⁴ is a C₁ -C₆ hydrocarbon group or --N═C(R⁷)₂ ;

each R⁵ and R⁷ is independently a C₁ -C₆ hydrocarbon group;

R⁶ is a H or a C₁ -C₆ hydrocarbon group;

n=1-2 and q=0-1, with the proviso that when X is N, n+q=1, and when X isS or 0, n+q=2;

u=the functionality of the polyol residue =0-6, with the proviso thatwhen u=0, the compound of Formula I is ##STR7## m=2-3; and z=1-3.

It is to be understood that each "R^(3--Si)(R⁵)_(3-m) (OR⁴)_(m) " moietycan be the same or different. When used in Formula I, the Y and R¹groups that are not symmetric, e.g., amide (--C(O)--NH--) andcarbamylthio (--S--C(O)--NH--) groups, are not limited to being bound toadjacent groups in the manner in which these groups are representedherein. That is, for example, if R¹ is carbamate (representedas--O--C(O)--NH--), it can be bound to Y and W in either of two manners:--Y--O--C(O)--NH--W-- and --W--O--C(O)--NH--Y--.

Herein, when it is said that "each" R⁵ and R⁷ is "independently" somesubstituent group, it is meant that generally there is no requirementthat all R⁵ groups be the same, nor is there a requirement that all R⁷groups be the same. As used herein, "substituted" means that one or morehydrogen atoms are replaced by a functional group that is nonreactive,e.g., to hydrolysis and/or condensation and noninterfering with theformation of the cured polymer.

In preferred materials R¹ is selected from the group consisting of asubstituted or unsubstituted C₁ -C₂₀₀ alkyl, a substituted orunsubstituted C₁ -C₂₀₀ acyl, and groups of up to 50 multiples of a C₃-C₁₈ cycloalkyl, a C₇ -C₂₀ aralkyl, and a C₆ -C₁₈ aryl. By this, it ismeant that R¹ can be a long chain containing, for example, up to 50repeating C₆ -C₁₈ aryl groups. More preferably, R¹ is selected from₃ thegroup consisting of a substituted or unsubstituted C₁ -C₁₀₀ alkyl, asubstituted or unsubstituted C₁ -C₁₀₀ acyl, and groups of up to 30multiples of a C₅ -C₈ cycloalkyl, and a C₆ -C₁₀ aryl. Most preferably,R¹ is selected from the group consisting of a C₁ -C₂₀ alkyl, a C₁ -C₈acyl, and groups of up to 5 multiples of a C₅ -C₈ cycloalkyl, and a C₆-C₁₀ aryl. In each of the preferred R¹ groups, the backbone isoptionally interrupted by 1-20 nonperoxide --O--, --C(O)--, --S--, --SO₂--, --NR₆ amide, ureido, carbamate, carbamylthio, allophonate, biuret,and isocyanurate groups.

In each of the more preferred R¹ groups, the backbone is optionallyinterrupted by 1-10 nonperoxide --O--, --C(O)--, --S--, --SO₂ --, --NR⁶--, amide, ureido, carbamate, carbamylthio, allophonate, biuret, andisocyanurate groups. In each of the most preferred R¹ groups, thebackbone of each of the R¹ groups is not interrupted by any of thesegroups.

In preferred materials, each of R² and R³ is independently selected fromthe group consisting of a substituted or unsubstituted C₁ -C₂₀ alkyl, asubstituted or unsubstituted C₂ -C₁₈ alkenyl, and groups of up to 10multiples of a C₃ -C₁₈ cycloalkyl and a C₆ -C₁₈ aryl. More preferably,each R² and R³ is independently selected from the group consisting of asubstituted or unsubstituted C₁ -C₁₀ alkyl, a substituted orunsubstituted C₂ -C₁₀ alkenyl, a C₅ -C₈ cycloalkyl, and a C₆ -C₁₀ aryl.Most preferably, each R² and R³ is independently selected from the groupconsisting of a C₁ -C₆ alkyl, a C₂ alkenyl, a C₅ -C₈ cycloalkyl, and aC₆ aryl. In each of the preferred R² and R³ groups, the backbone isoptionally interrupted by 1-5 nonperoxide --O--, --C(O)--, --S--, --SO₂--, and --NR⁶ -- groups. In optimal resins, the backbone of each of theR² and R³ groups is not interrupted by any of these groups.

In preferred materials, each of R⁴, R⁵, R⁶, and R⁷ is independently a C₁-C₆ alkyl group. More preferably, each is a C₁ -C₃ alkyl group. A singleprepolymer according to Formula I can be used in the resin compositionof the present invention. Alternatively, a mixture of several differentprepolymers according to Formula I can be used in the resin composition.

Optionally, the scrims of the present invention are coated with a resinwhich incorporates microfiber fillers. These preferred orthopedicbandages enjoy many benefits, for example, resins which incorporatemicro fiber fillers exhibit: a dramatic increase in strength when coatedon the backings of the present invention; an increased "early strength"upon curing; an improved durability and increased modulus; betterlayer-to-layer lamination strength; a lower exotherm upon setting; and alower effective resin cost compared to resins which do not incorporatesuch microfiber fillers. In addition, resin suspensions employing themicrofiber fillers of the present invention exhibit generally verylittle increase in resin viscosity--thereby ensuring easy unwind of thecasting bandage and good handling properties such asdrapability.Suitable microfibers for use in the present inventioninclude those micro fiber fillers disclosed in U.S. patent applicationSer. No. 08/008,755 which is herein incorporated by reference.

In addition to the application of the present invention to the field oforthopedic casting tapes, other uses may include wrapping and/or joiningpipes, cables or the like; patching or bridging gaps to provide asurface for filling and repairs; etc.

The following examples are offered to aid in understanding of thepresent invention and are not to be construed as limiting the scopethereof. Unless otherwise indicated, all parts and percentages are byweight.

EXAMPLES

Ring strength was measured as described in the following procedure. Acylindrical ring comprising 6 layers of the resin-coated material wasformed by taking a roll of the resin-coated material from its storagepouch and immersing the roll completely in deionized water having atemperature of about 27° C. for about 30 seconds. The width of the ringformed was the same as the width of the resin-coated material employed,namely, 7.62 cm. The roll of resin-coated material was then removed fromthe water and the material was wrapped around a 5.08 cm diameter mandrelcovered with a thin stockinet (such as 3M Synthetic Stockinet MS02) toform 6 complete uniform layers using a controlled wrapping tension ofabout 45 grams per centimeter width of material. Each cylinder wascompletely wound within 30 seconds after its removal from the water.

After 7 to 20 minutes from the initial immersion in water, the curedcylinder was removed from the mandrel. Ring strength was determined 24hours after initial immersion in water, i.e., those samples were allowedto cure for 24 hours in a controlled atmosphere of 25° C. ±2° C. and55%±5% relative humidity prior to testing.

At the appropriate time each cylinder was then placed in a fixture in acommercial testing machine, e.g., an Instron 1122 instrument, andcompression loads were applied to the cylindrical ring sample along itsexterior and parallel to its axis. The cylindrical ring was placedlengthwise between the two bottom bars of the fixture (the bars being1.9 cm wide, 1.3 cm in height, and 15.2 cm long), with the bars spacedabout 4 cm apart. The inside edges of the bars were machined to form acurved surface having a 0.31 cm radius. A third bar (0.63 cm wide, 2.5cm high, and 15.2 cm long) was then centered over the top of thecylinder, also parallel to its axis. The bottom or contacting edge ofthe third bar was machined to form a curved surface having a 0.31 cmradius. The third bar was brought down to bear against and crush thecylinder at a speed of about 5 cm/min. The maximum force which wasapplied while crushing the cylinder was then recorded and divided by thewidth to yield the "ring strength," which in this particular instance isthe "dry strength" (expressed in terms of force per unit length of,thecylinder, i.e., newtons/cm). For each material, at least 5 samples weretested, and the average peak force applied was then calculated andreported as the dry "ring strength."

To measure the "wet ting strength", the same procedure was followed asfor the "dry ring strength", except that after curing for 24 hours, thecylinder was then immersed in water at about 45° C. for about 30minutes, and then allowed to dry at room temperature and pressure forabout 15 minutes. The cylinder was then placed in the instrument andcrushed as described hereinabove in order to determine the "wet ringstrength" thereof.

To measure the "warm wet ring strength" of the cylinder, the procedurewas followed exactly as set forth for the "wet ting strength"measurement above, with the exception that the cylinder was placed inthe fixture and crushed immediately after removal from the 45° C. waterbath and was not allowed to dry at all.

Ring delamination was measured as described in the following procedure.A cylindrical ring comprising 6 layers of the resin-coated material wasformed by taking a roll of the resin-coated material from its storagepouch and immersing the roll completely in deionized water having atemperature of about 27° C. for about 30 seconds. The width of the tingformed was the same as the width of the resin-coated material employed,namely, 7.62 cm. The roll of resin-coated material was then removed fromthe water and the material was wrapped around a 5.08 cm diameter mandrelcovered with a thin stockinet (such as 3M Synthetic Stockinet MS02) toform 6 complete uniform layers using a controlled wrapping tension ofabout 45 grams per centimeter width of material. A free tail of about15.24 cm was kept and the balance of the roll was cut off. Each cylinderwas completely wound within 30 seconds after its removal from the water.

After 15 to 20 minutes from the initial immersion in water, the curedcylinder was removed from the mandrel, and after 30 minutes from theinitial immersion in water its delamination strength was determined.

A determination of delamination strength was done by placing the freetail of the cylindrical sample in the jaws of the testing machine,namely, an Instron Model 1122 machine, and by placing a spindle throughthe hollow core of the cylinder so that the cylinder was allowed torotate freely about the axis of the spindle. The Instron machine wasthen activated to pull on the free tail of the sample as a speed ofabout 127 cm/min. The average force required to delaminated the wrappedlayers over the first 33 centimeters of the cylinder was then recordedin terms of force per unit width of sample (newtons/cm width). For eachmaterial, at least 5 samples were tested, and the average delaminationforce was then calculated and reported as the "delamination strength."

Example 1

Shrink Yarns for Use in Compaction of a Fiberglass Knit Casting Tape

Most synthetic polymeric fibers exhibit some degree of shrinkage whenheated. In order to be useful in the present invention the heat shrinkfibers should generate a sufficient force and a sufficient displacementduring their shrinkage to adequately compact the knit tape. Suitableheat shrink fibers are preferably capable of performing this compactionwhen present in an amount that can be successfully desized withoutcausing excessive degradation of the fiberglass (e.g., present at arelatively low denier).

The percent shrinkage and shrinkage force for the following commerciallyavailable yarns was measured as a function of temperature.

                  TABLE 1a    ______________________________________    Yarn             Denier  Composition    ______________________________________    Dupont.sup.1 440-100-R02-52                     440     Multifilament Polyester    Dupont 220-50    220     Multifilament Polyester    Celanese.sup.2 90/36, T770 brt,                     90      Multifilament Polyester    1/4 turn    Celanese 100/33  100     Multifilament Polyester    Shakespeare.sup.3 MX-306                     340     Monofilament    0.009 401 1010 10A (LDPE)                             polyethylene    Shakespeare 283  283     Monofilament Polyester    ______________________________________     .sup.1 Dupont, Fibers Div. Wilmington DE     .sup.2 Celanese Fibers, Celanese Chemical Co., New York, NY     .sup.3 Shakespeare Monofilament Div., Columbia, S.C.

The data presented in Tables 1b and 1c was generated using a Testrite™MK IV Shrinkage-Force Tester (available from Testrite Ltd., WestYorkshire, England). Percent shrinkage was measured using the followingtest method. The Testrite™ apparatus was preheated to the desiredtemperature range and a sample of yarn about 600 mm long was clamped atone end to the fixed jaw clamp and allowed to drape over the take updrum. A clip weight (1.78 gin) was attached to the other end of the yarnand allowed to hang about 100 mm below the center of the drum. Thisweight is used primarily to take out the catenary from the sample. Withthe sample in position on the drum, the drum was rotated so the digitalreadout displays 0 (zero). The carriage assembly was then carefullypushed forward slowly into position in the heat zone. The heat willcause the sample to shrink and thus rotate the take up drum. Maximumshrinkage of the sample at any given operating temperature is deemed tohave taken place when the digital readout holds steady.

Shrinkage force was similarly measured according to the following test.The Testrite™ apparatus was fitted with the load cell and jaw attachmentapparatus secured to the carriageway. The sample was secured to thefixed jaw clamp and draped over the take up drum as previouslydescribed. After removing the catenary from the sample (e.g., by hanginga 1.78 gm weight from the free end of the sample) the load cell clampwas secured to the sample. The carriage assembly was then carefullypushed forward slowly into position in the preheated heat zone. The heatwill cause the sample to shrink and thus apply tension to the load cell.Maximum shrinkage force of the sample at any given operating temperatureis then recorded.

                  TABLE 1b    ______________________________________    Percent Shrinkage for Various Yarns    Temp   DuPont    Celanese  Celanese                                       Shakespeare    (°C.)           440       90        100     MX-306    ______________________________________    50     --        --        --      3    60     --        --        --      7    70     --        --        --      14    80     --        --        --      16    90     --        --        --      18    100    --        --        --      21    110    --        --        --      --    120    --        --        --      --    130    6         5         --      --    140    8         6         --      --    150    10        7         --      --    160    11        8         11      --    170    13        9         12      --    180    14.5      10.5      11      --    190    16        12        14      --    200    19        14        14      --    210    21        10        15      --    220    24.5      20        16      --    230    27        24        20      --    240    --        29        24      --    250    --        --        28      --    ______________________________________

Table 1b depicts the percentage of shrinkage for various organic yarnswhich have been subjected to a heat cycle. As can be readily observed(and within the temperature ranges shown) the yarns generally exhibitmore shrinkage as they are heated to higher temperatures. Notably, the"Shakespeare MX-306" yarn (comprising a polyethylene polymer) exhibitsits shrinkage at a lower temperature than the other yarns (which eachcomprise a polyester polymer).

                                      TABLE 1c    __________________________________________________________________________    Shrinkage Force For Various Yarns (N)    Temp        Celanese.sup.1              Celanese.sup.2                    Celanese.sup.3                          DuPont                               DuPont                                    Shakespeare    (°C.)        90    90    90    220  440  PX-301    __________________________________________________________________________    140 0.3   0.7   1     0.7       0.7    150 0.3   0.6   1.1   0.7       1.0    160 0.3   0.7   1.1   0.8       1.0    170 0.2   0.8   1.1        0.8  1.1    180 0.4   0.7   1.2   0.7  1.5  1.1    190 0.3   0.6   1.2   0.6  1.4  1.1    200 0.1   0.8   1.2   0.6  1.3  1.0    210 0.1   0.8   0.9   0.5  1.3  0.9    220 0.3   0.5   1.1   0.6  1.3  0.8    230 0.3   0.7   1.1        1.2  0.7    __________________________________________________________________________     .sup.1 One yarn.     .sup.2 Two yarns.     .sup.3 Three yarns.

Table 1c depicts the shrinkage force (Newtons) for various organicyarns. These yarns were preloaded with a weight of approximately 1.73 gprior to testing. The data for the Celanese 90 denier 36 filament yarnshown in Table 1c indicates that the shrink force is generallyproportional to the number of yarns used.

Example 2

Compaction of a Fiberglass Knit Casting Tape

Several of the yarns from Example 1 were inserted into a fiberglass knitstructure and used to compact the knit structure. The yarns were placedin as a single needle lay-in in a fiberglass fabric with the followingparameters: Mayer Raschel 60 inch knitter (available from Meyer TextileMachinery Corp., Greensboro, N.C. as HDR10EHW ); 18 gauge (7.09needles/cm); front runner length (chain stitch) 403.9 cm; back runnerlength Gay-in stitch) 355.6 cm; and middle runner length (shrink yarnlay-in stitch) 91.4 cm. Owens Corning fiberglass (available from OwensCorning, Aiken, S.C. as ECG 75 1/0 0.7Z 620) was used for both the frontand back bar.

Heat shrink yarns were inserted into the knit using a third bar (i.e.,the middle bar as previously described). As described below, the heatshrink yarns were not placed in every wale but were spaced into aboutevery third or every sixth wale. The fabrics had the following physicalproperties: 10.4 cm width; 5.39 courses per cm; and 29.6 gm per meterlength.

The fabric was heat shrunk using forced hot air and then wound up."Percent compaction" was measured by first marking off a known length offabric and measuring the length after heat treatment. Note that themarked off section was positioned in the middle of a longer piece offabric in order to ensure that the heat shrink yarn would not slipduring compaction. The percent compaction was calculated as: ##EQU1##The following table summarizes the results:

                  TABLE 2a    ______________________________________              Peak shrink        In-laid                                       Percent    Yarn      force.sup.1, (N)                        Denier   every:                                       compaction (%)    ______________________________________    Dupont 440              1.5       440      6 wales                                       15-18%    Celanese 90    1 end     0.4       90    2 ends    0.8       180    3 ends    1.2       270      6 wales                                       10-12%                                 3 wales                                       < 10%    Shakespeare              1.1       283      6 wales                                       >15%    PX-301                       3 wales                                       >15%    Shakespeare              1.5       340      6 wales                                       17-20%    MX-306    ______________________________________     .sup.1 Tested as, described in Example 1.

The above data indicates that in order to compact the fabric of thisspecific construction a force greater than about 1N is desirable.Furthermore, the data suggests that a monofilament of equivalent denierappears to yield greater compaction than a multifilament yarn.

Example 3

Effect of Winding Tension

A 7.62 cm knitted fiberglass fabric containing Dupont 440-100-R02-52multifilament polyester shrink yarn was produced with the followingparameters: Owens Corning fiberglass EGG 75 1/0 620; heat shrink yarn:Dupont 440-100-R02-52 polyester; Mayer Raschel 229 cm 18 gauge (7.1needles/cm) knitter; knit pattern: 0/2, 2/0 (front bar); 0/0, 2/2(middle bar); and 6/6, 0/0 (back bar); thread up: front and back-full,middle bar: single needle in-lay spaced every 6th wale; front runnerlength (fiberglass chain stitch) 406 cm; back runner length (fiberglasslay-in stitch ) 274 cm; middle bar runner length (polyester heat shrinklay-in stitch ) 86.4 cm. Owens Corning fiberglass (available from OwensCorning, Aiken, S.C. as ECG 75 1/0 620) was used for both the front andback bar. Note that the heat shrink yarn was in-laid 180 degrees out ofphase with the fiberglass in-lay and across a single needle in analternating pattern of: 1 wale in and the next five wales out. The exactmiddle bar threading was (1,5,1,5,1,5,1,5,1,4,1,5,1,5,1,5,1,5,1) where 1indicates a wale containing a heat shrink yarn, 4 indicates 4 waleswithout the heat shrink yarn, and 5 indicates 5 wales without the heatshrink yarn.

In order to determine the effect of wind-up tension on the temperaturereached during desiring within a rolled up "jumbo" of fabric thefollowing experiment was conducted.

A sample of approximately 27.4 meters of the knit structure was wound byhand into either a "tight" or a "loose" roll. The fight roll wasproduced by winding the knit as tightly as could be performed by handwithout plastically deforming the heat shrunk yarn. The loose roll wasproduced by applying very little tension to the knit during windup. Thetightly wound roll had a circumference of approximately 36.5 cm and theloosely wound roll had a circumference of approximately 44.0 cm. Duringthe winding operation two small plastic tubes were inserted between thelayers (as guides for inserting thermocouple sensors), the firstapproximately at the middle of the roll diameter (i.e., near the core)and the second at approximately 1.3 cm from the outer edge. The plasticguides were removed prior to desizing. The rolls were placed in a forcedair recirculating oven in separate cycles. The oven was brought up to500° C. and held for 8 to 10 hours at that temperature. The temperatureof the roll was recorded as a function of time. Peak temperatures areshown below:

                  TABLE 3a    ______________________________________             Position:             Mid roll            Outer 1 cm    Roll     Peak temp.                       Time      Peak temp.                                         Time    Tension  (°C.)                       (min.)    (°C.)                                         (min)    ______________________________________    Tight    571       76        544     60    Loose    720       62        549     32    ______________________________________

The data indicates that both rolls heated up significantly higher thanthe oven temperature. The data also indicates that the loosely woundroll became significantly hotter in the center of the roll than thetightly wound roll. This higher temperature could lead to degradation ofthe fabric integrity. The loosely wound roll also reached its peakexotherm temperature more quickly than the tightly wound roll. Althoughnot intending to be bound by theory, these results are believed to be inpart due to the different amounts of oxygen available within the roll.The oxygen being necessary for the combustion of the heat shrink yarnand affecting the combustion rate.

Notably, an important advantage of using heat shrink yarns to impartcompaction to a knit fabric is the ability to wind the knit fabric undertension while not thereby removing the extensibility.

Example 4

Coated Fabric

A 10.2 cm knit produced with the knitting parameters shown in Ex. 3 washeat shrunk in a tunnel oven at a temperature of 218° C. The fabric wasobserved to shrink approximately 15% during this heat treatment process.The shrunken fabric was then wound into a fairly loose roll under lowtension. In order to avoid sagging in the oven which would reduce thecompactness of the fabric the roll was supported by wrapping fiberglassfabric through the aluminum core and around the exterior of the roll.This wrap served to support the weight of the fabric and preventundesirable sagging.

The tape was heat set and cleaned in a recirculating hot air oven at427° C. for 8 hours. The heat set fabric was coated using a very lowtension coater with the following isocyanate functional prepolymerresin:

                  TABLE 4a    ______________________________________    Chemical       Manufacturer Eqwt.   Wt. %    ______________________________________    Isonate 2143L  Dow Chemical 144.7   57.7    pToluenesulfonyl chloride                   Akzo                 0.05    Antifoam DB-100                   Dow Corning          0.18    Butylated hydroxytoluene                   Shell Chemical       0.48    Pluronic F-108 BASF                 4.00    MEMPE          3M                   1.15    PPG-2025       Union Carbide.sup.1                                1019.25 21.22    LG-650         Union Carbide.sup.1                                85.49   5.67    Niax E-562     Union Carbide.sup.1                                1753.13 9.55    ______________________________________     .sup.1 Formerly available from Union Carbide now available from Arco     Chemical Co., So. Charlestown, WV

The resin was coated on the 10.2 cm wide fabric produced as describedabove at a coating weight of 40% by weight. The product was rolled up ona 1.27 cm diameter polyethylene core into individual rolls approximately320 cm long and the rolls were sealed in conventional moisture proofaluminum foil laminate pouches. The product was tested for theproperties listed below according to the test methods described above.All values are the mean of 5 samples unless otherwise noted.

                  TABLE 4b    ______________________________________    Test                Result    ______________________________________    Ring delamination.sup.1                         8.9 N/cm width    Dry Strength        79.5 N/cm    Wet Strength        42.0 N/cm    Warm Wet Strength   25.6 N/cm    ______________________________________     .sup.1 Three samples tore before a delamination value could be recorded.     The result shown is an average of the two samples that did not tear.

Example 5

Desize Cycle Optimization

In order to prevent degradation of the fabric it is important to keepthe temperature in the jumbo as low as possible while still removing theyarn and combustion products completely. This experiment investigatedvarious temperature profiles in the oven cycle and the effect oninternal fabric temperatures.

A 7.62 cm knitted fiberglass fabric containing Dupont 440-100-R0252-52multifilament polyester shrink yarn was produced with the followingparameters: Owens Corning fiberglass ECG 75 1/0 620; heat shrink yarn:Dupont 440/100/R02/52 polyester; Mayer Rasehel 229 cm knitter; 18 gauge(7.1 needles/cm); knit pattern: 0/2, 2/0 (front bar); 0/0, 2/2 (middlebar); and 8/8, 0/0 (back bar); thread up: front and back-full, middlebar: single needle in-lay spaced every 6th wale; front runner length(fiberglass chain stitch ) 406 cm; back runner length (fiberglass lay-institch) 368 cm; middle bar runner length (polyester heat shrink lay-institch) 96.5 cm. Owens Corning fiberglass (available from Owens Corning,Aiken, S.C. as ECG 75 1/0 620) was used for both the front and back bar.Note that the heat shrink yarn was in-laid 180 degrees out of phase withthe fiberglass in-lay and across a single needle in an alternatingpattern of: 1 wale in and the next five wales out. The exact middle barthreading was (1,5,1,5,1,5,1,5,1,4,1,5,1,5,1,5,1,5,1) where 1 indicatesa wale containing a heat shrink yarn, 4 indicates 4 wales without theheat shrink yarn, and 5 indicates 5 wales without the heat shrink yarn.

The tape produced had a nominal 10.2 cm width and was wound up using asurface winder to a roll diameter of approximately 45.7 cm. The fabricshad the following physical properties: 10.4 cm width; 5.79 courses percm; and a weight of 16.6 gm per 240 courses.

The rolls were heat shrunk by passing the material as a single layerthrough a tunnel oven (approximately 1 meter in length) set at atemperature of 249° C. at a speed of 96.5 cm/min. and supported on ametal belt conveyor. After heat shrinking the tape was wound back upinto roll form on a 7.62 cm diameter aluminum roll. Individual rollswere heat set and cleaned in a small recirculated oven. The temperaturecycles were varied and the temperature monitored using a set ofthermocouples. Thermocouples were placed between layers of fabric atradial positions approximately 10, 50, and 90% of the roll length awayfrom the core of the roll. The peak temperatures reached at each ofthese points for each cycle are presented below:

                  TABLE 5a    ______________________________________    Oven operating conditions                         Peak temperature of roll    Run  temperature cycle time  at position indicated    #    (°C.)                     (hours)     10%   50%   90%    ______________________________________    1    399         8           532   538   460    2    427         8           552   554   521    3    399         8           552   552   518    4    343° C. for 4 hours, then 427° C.                             510     532   488         for 4 hrs    5    371° C. for 4 hours, then 427° C.                             468     496   438         for 4 hrs    ______________________________________

After treatment in the oven all the materials were observed to be clean.Run 5 is presently preferred.

Example 6

Effect of Heat Shrink Yarn on Web Integrity

Samples of heat set cleaned fabric similar to that described in Ex. 4were studied to determine whether there is any localized degradation ofthe fiberglass due to the added combustible heat shrink yarn (DuPont 440yarn). The fabric samples were sized by immersing the fabric in a 1%aqueous solution of Triple Concentrate Downy™ fabric softener (availablefrom Proctor and Gamble Co., Cincinnati, Ohio). Samples were taken fromthe midpoint of the roll which had been exposed to the operatingconditions of Run #5 of Table 5a. Wales at selected positions across thewidth of the tape were removed and tested for tensile strength using anInstron model 1122 testing machine (Instron Corp., Park Ridge, Ill). Theaverage value of three samples is shown below in Table 6a.

                  TABLE 6a    ______________________________________    Wale number   Tensile strength (N)    ______________________________________    1.sup.1       4.89    2             6.14    3             7.47    4             6.67    5             6.23    6             7.47    7.sup.1       6.14    8             5.60    9             6.32    10            7.92    11            9.12    12            6.72    13.sup.1      4.45    14            6.14    15            8.10    16            9.12    17            7.03    18            5.43    19.sup.1      --    ______________________________________     .sup.1 A heat shrink yarn was inserted at these wale positions.

The results clearly show that near the local vicinity of a heat shrinkyarn the fiberglass yarns are degraded. While not intending to be boundby theory, this result is believed to be due to the fiberglass yarnhaving been exposed to a higher localized temperature caused by thecombustion of the heat shrink yarn.

Similar knits to the above knit were produced except that the heatshrink yarn was replaced with three yarns in each position of theCelanese 90 denier polyester shrink yarn (C90) or with a single yarn ofthe Shakespear PX-301 283 denier polyester monofilament (PX-301). Notethat the PX-301 knit was only 7.62 cm wide and was not heat shrunk priorto heat setting. The individual wale tensile strengths for these fabricsis shown below in Table 6b:

                  TABLE 6b    ______________________________________                  Tensile strength (N)                    Celanese Shakespear    Wale number     C90      PX301    ______________________________________    6.sup.1         8.1      9.4    7               9.9      9.1    8               10.9     9.3    9               11.4     13.7    10              12.1     8.5    11              12.1     9.5    12.sup.1        9.0      9.2    13              9.3      8.5    14              8.9      11.4    15              8.1      9.0    16              12.2     11.7    17              9.0      9.0    18.sup.1        8.4      8.8    ______________________________________     .sup.1 A heat shrink yarn was inserted at these wale positions.

Note that the C90 sample shows loss of integrity near the local areaaround the heat shrink yarn. The PX-301 sample, however, does not showthis effect as clearly. Note that all of the wale strength values aresignificantly higher than for the knit containing the Dupont 440 denierpolyester.

A similar experiment was conducted using Shakespear MX-306 polyethylenemonofilament and no heat shrink yarn (control). For all materials asample of fabric was also stretched in tensile in the Instron 1122 andthe load at which wide breakage occurred was recorded. A summary of thedata is given in the table below (values recorded in Newtons). Allvalues are mean values of at least three trials.

                                      TABLE 6c    __________________________________________________________________________                     DuPont                          Celanese                               Shakespear                                     Shakespear                     440  C90  PX301 MX306    Test        Control                     (440d)                          (270d)                               (283d)                                     (340d)    __________________________________________________________________________    Fabric Stretch Test                53-76                     18-22                          31-53                               18-27 44-53.sup.1    load at wale break    Indiv. wale tensile                12.5 4.4  8.0  8.9   6.7    (wale w/ shrink yarn)    Indiv. wale tensile,                12.5 8.9  12.2 13.3  6.7    (wales w/o shrink yarn)    __________________________________________________________________________     .sup.1 Individual wales did not break before the fabric ripped at the     clamp site.

The data clearly shows that the fabrics containing the lower denierpolyester materials (C90 or PX-301) retain much more integrity than thefabric containing the higher denier polyester heat shrink yarn (Dupont440).

Example 7

Fabric compacted with a multifilament POY yarn

A 7.62 cm knitted fiberglass fabric containing Celanese partiallyoriented yarn (hereinafter "POY") was produced with the followingparameters: Owens Corning fiberglass ECG 75 1/0 620; heat shrink yarn:Celanese POY Style 661,227 denier; Mayer Raschel 229 cm knitter; 18gauge (7.0866 needles/cm); knit pattern: 2/0,0/2 (front bar); 0/0,2/2(middle bar); and 0/0,8/8 (back bar); thread up: front and back-full;middle bar: single needle in-lay spaced every third wale; front runnerlength (fiberglass chain stitch ) 419 cm; back runner length (fiberglasslay-in stitch ) 338 cm; take-up length per rack: 94 cm.

Owens Corning fiberglass (available from Owens Corning, Aiken, S.C. asECG 75 1/0 620) was used for both the front and back bar. Note that theheat shrink yarn was in-laid in phase with the fiberglass in-lay andacross a single needle in an alternating pattern of: 1 wale in and thenext two wales out. The exact middle bar threading was(0101001001001001001001001001001001001001001001001001001010) where 1indicates a wale containing a heat shrink yarn and 0 indicates waleswithout the heat shrink yarn.

A nominal 10.2 cm fabric was produced and wound up by hand. The fabricwas heat shrunk by heating with saturated 10.3N/cm² steam. The fabriccontracted about 12-15%. Once desized the knit would have between about40 and 45% extensibility.

Various modifications and alterations of this invention will be apparentto those skilled in the art without departing from the scope and spiritof this invention, and it should be understood that this invention isnot limited to the illustrative embodiments set forth herein.

What is claimed is:
 1. An article, comprising:a compacted fiberglassknit fabric sheet, wherein said fabric comprises adjacent rows ofoverlapping loops, said fabric being compacted using a heat shrink yarn;and a curable or hardenable liquid resin coated onto said compactedfabric sheet.
 2. An article according to claim 1, wherein said coatedfabric further comprises a heat shrunken yarn.
 3. An article accordingto claim 1, wherein said heat shrink yarn is selected from the groupconsisting of polyester, polyamide and polyethylene.
 4. An articleaccording to claim 1, wherein said heat shrink yarn shrinks at atemperature between 70° C. and 300° C.
 5. An article according to claim3, wherein said heat shrink yarn is knit into said fabric as a lay-in.6. An article according to claim 3, wherein said sheet has from about25% to about 75% extensibility in the elongated direction when a 268gram load or force is applied across a 1 cm section of the fabric.
 7. Anarticle according to claim 1, wherein said curable resin is selectedfrom the group consisting of water-curable resins comprising awater-reactive liquid organometallic compound and an organic polymer,alkoxysilane terminated polyurethane prepolymer resins, andisocyanate-functional resins.
 8. An article according to claim 1,wherein said curable resin is a water-curable resin comprisingisocyanate-functional resins.
 9. An article according to claim 3,wherein said fabric has between about 6 and 70 openings per square cmwhen under a tensile load of 2.63 N/cm width.
 10. An article accordingto claim 1, wherein said fabric was compacted to between about 30 and 90percent of its original dimension.
 11. An article according to claim 1,wherein said fabric was compacted to between about 50 and 80 percent ofits original dimension.
 12. An article according to claim 8, whereinsaid resin has a viscosity between about 10 Pa s and 100 Pa s.
 13. Anarticle according to claim 3, wherein said heat shrink yarn has a denierbetween 100 and
 500. 14. An article according to claim 5, wherein saidheat shrink yarn has a denier between 200 and
 300. 15. An article,comprising:a compacted fiberglass knit fabric sheet, wherein said fabricsheet comprises adjacent rows of overlapping loops, said fabric beingcompacted using a heat shrink yarn, wherein said heat shrink yarn isknit into said fabric sheet as a lay-in; and a water-curableisocyanate-functional resin coated onto said compacted fabric sheet. 16.An article according to claim 15, wherein said heat shrink yarn has adenier between 200 and 300, shrinks at a temperature between 70° C. and300° C. and is selected from the group consisting of polyester,polyamide and polyethylene.
 17. An orthopedic casting bandage,comprising:a compacted fiberglass knit fabric sheet, wherein said fabriccomprises adjacent rows of overlapping loops, said fabric beingcompacted using a heat shrink yarn; and a water-curableisocyanate-functional resin coated onto said compacted fabric sheet. 18.An orthopedic casting bandage according to claim 17, wherein said heatshrink yarn shrinks at a temperature between 70° C. and 300° C. and isselected from the group consisting of polyester, polyamide andpolyethylene.
 19. An orthopedic casting bandage according to claim 17,wherein said fabric sheet has from about 25% to about 75% extensibilityin the elongated direction when a 268 gram load or force is appliedacross a 1 cm section of the fabric sheet.
 20. An orthopedic castingbandage according to claim 17, wherein said fabric has between about 6and 70 openings per square cm when under a tensile load of 2.63N/cmwidth, and wherein said resin has a viscosity between about 10 Pa s and100 Pa s.